Can't get AJAX Calendar Extender to work in DotNetNuke

See more:

Ajax

Some helpful info:
DotNetNuke 5.4.1
AjaxControlToolkit 3.5.40412
.NET 3.5
Visual Studio 2008

I've written several DotNetNuke modules, but this is the first time I've tried to incorporate any extenders from the Ajax Control Toolkit.

I've reduced the current module to just a textbox and a calendar extender and I can't get the extender to work. The module loads, but I get a bunch of javascript errors on the page. The most descriptive message is:

AjaxControlToolkit requires ASP.NET Ajax 4.0 scripts. Ensure the correct version of the scripts are referenced. If you are using an ASP.NET ScriptManager, switch to the ToolkitScriptManager in AjaxControlToolkit.dll.

I've tried a few things already, but nothing seems to be working.

Ideas?
Markup:

<%@ Control language="vb" Inherits="jec.Modules.jec_AjaxTest1.Viewjec_AjaxTest1" AutoEventWireup="false" Explicit="True" Codebehind="Viewjec_AjaxTest1.ascx.vb" %>
<%@ Register assembly="AjaxControlToolkit" namespace="AjaxControlToolkit" tagprefix="asp" %>

<div>
    <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
    <asp:CalendarExtender ID="TextBox1_CalendarExtender" runat="server"
        Enabled="True" TargetControlID="TextBox1">
    </asp:CalendarExtender>
</div>

Codebehind:

Imports System.Web.UI
Imports System.Collections.Generic
Imports System.Reflection

Imports DotNetNuke
Imports DotNetNuke.Services.Exceptions
Imports DotNetNuke.Services.Localization

Namespace jec.Modules.jec_AjaxTest1

    Partial Class Viewjec_AjaxTest1
        Inherits Entities.Modules.PortalModuleBase

#Region "Event Handlers"
         Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
            Try

            Catch exc As Exception        'Module failed to load
                ProcessModuleLoadException(Me, exc)
            End Try
        End Sub

#End Region

    End Class

End Namespace